Addition Of Ground Tire Rubber Research Articles

Fatigue Property Evaluation of Sustainable Porous Concrete Modified by Recycled Ground Tire Rubber/Silica Fume under Freeze-Thaw Cycles

As an environmentally friendly pavement material, porous concrete in seasonal frozen region is often subjected to repeated loads and freeze-thaw cycles. Therefore, the fatigue property of porous concrete under freeze-thaw is extremely important. However, few researches have been reported on the topic. Based on this background, this paper investigates the flexural fatigue property of ground tire rubber/silica fume composite modified porous concrete (GTR/SF-PC) with experimental and mathematical statistical methods. The flexural fatigue life of GTR/SF-PC under different freeze-thaw cycles (0, 15, 30) was tested with three-point flexural fatigue experiment at four stress levels (0.70, 0.75, 0.80, 0.85). Kaplan Meier survival analysis and Weibull model were adopted to analyze and characterize the flexural fatigue life. The fatigue life equations of GTR/SF-PC under different freeze-thaw cycles were established. The results indicate that, duo to the addition of ground tire rubber and silica fume, the static flexural strength of GTR/SF-PC is not significantly affected by freeze-thaw cycles. The flexural fatigue property of GTR/SF-PC is gradually deteriorated under the action of freeze-thaw cycles. Compared with 0 freeze-thaw cycles, the average flexural fatigue life of GTR/SF-PC decreases about 15% and the fatigue failure rate increases about 50% after 30 freeze-thaw cycles, respectively. The fatigue equations with different reliabilities of GTR/SF-PC show that the reliability is inversely proportional to fatigue life, therefore, the appropriate fatigue equation considering freeze-thaw effect is necessary for fatigue design of porous concrete.

Ground tire rubber/polyamide 6 thermoplastic elastomers produced by dry blending and compression molding

This study investigates the addition of ground tire rubber (GTR) into virgin polyamide 6 (PA6) to produce thermoplastic elastomer (TPE) blends. In particular, a wide range of GTR concentration (0–100% wt.) was possible by using a simple dry blending technique of the materials in a powder form followed by compression molding. The molded samples were characterized in terms of morphological (scanning electron microscopy), physical (density and hardness) and mechanical (tension, flexion and impact) properties. The results showed a decrease in tensile and flexural moduli and strengths with GTR due to its elastomeric nature. However, significant increases were observed on the tensile elongation at break (up to 167%) and impact strength (up to 131%) compared to the neat PA6 matrix. Based on the results obtained, an optimum GTR content around 75% wt. was observed which represents a balance between high recycled rubber content and a sufficient amount of matrix to recover all the particles. These results represent a first step showing that a simple processing method can be used to produce low cost PA6/GTR compounds with a wide range of physical and mechanical properties.

Reuse of ground tire rubber (GTR) as a filler of TPE matrix*

Used car tires are the type of waste that does not decompose naturally and is not recyclable in molten state. Despite many initiatives to reuse these materials on a global scale, a large part of used tires are still landfilled. The present work is an attempt to use ground powder of ground tire rubber (GTR) to filling the TPE-S thermoplastic elastomer matrix. The aim of this study was to obtain TPE-GTR compositions in standard thermoplastic processing machines. This study used rubber powder with a grain size of 0.2-0.4 mm, obtained by grinding process in a knife mill of own design. The GTR filler into the TPE matrix in the amount of 5 and 50 wt% was dosed. Specimens were produced by injection molding. The obtained molded parts were tested for tensile strength, Shore hardness and Schob elasticity. Influence of melt temperature on TPE-GTR molded parts properties was also examined. The addition of GTR to the matrix causes a significant decrease in elongation at break, while improving the stiffness, damping properties and hardness of the TPE-GTR composition. It was also found that the melting temperature above 200°C has negative effect on the properties of the TPE-GTR compounds.

Investigation of hot mixture asphalt with high ground tire rubber content

Stockpiles of waste tires pose concerns of potential contamination of local groundwater, and fire risk from the large amounts of tires. To sustainably use the waste tires, Ground Tire Rubber (GTR) that produced from waste tires has been used in the pavement industry for decades. The typical GTR content is approximately 1–3% by weight of the asphalt mixture. To utilize more waste tires, there is an increasing demanding of using higher amount of GTR in recent years. The objective of this study was to determine the high GTR content that can be used in the asphalt pavement without sacrificing performance. In this study, gap-graded mixtures modified with differing GTR contents were designed. These GTR contents were 2.6%, 3.4%, 3.7%, 4.1% and 4.5% by weight of the mixture. Statistical analysis was conducted to determine the influence of GTR content on the mixture performance. It was found that the fracture energy of the GTR modified mixture was two to three times higher than that of the control mixture. All of the mixtures seemed to provide adequate rutting resistance for low-volume traffic, signifying that after 5000 wheel passes, the rutting depth did not exceed the 12.5-mm. The GTR modified gap-graded mixtures had high resistance to low-temperature cracking and high-temperature rutting. This can partly be attributed to the addition of GTR and the skeleton structure from gap gradation. The result of multiple comparisons suggested that even though the addition of GTR in dense-graded mixtures did not significantly improve the high-temperature performance, the addition of GTR in asphalt mixtures significantly improved the low-temperature performance.

Giving a Second Opportunity to Tire Waste: An Alternative Path for the Development of Sustainable Self-Healing Styrene-Butadiene Rubber Compounds Overcoming the Magic Triangle of Tires.

Current regulations demand tires with long lifetime and reduced fuel consumption without sacrificing car safety. However, tire technology still needs to reach a suitable balance between these three indicators. Here, we address them by developing a self-healing tire compound using styrene–butadiene rubber (SBR) as the matrix and reclaimed tire waste as the sustainable filler. The addition of ground tire rubber (GTR) to the matrix simultaneously improved the rolling resistance and maintained both wet grip and healing ability. We provide an in-depth analysis of the healing behavior of the material at a scale close to the relevant molecular processes through a systematic dynamic-mechanical and dielectric analysis. We found that SBR and SBR/GTR compounds show a complete recovery of stiffness and relaxation dynamics after being damaged by cyclic deformation, resulting in a heterogeneous repaired rubber network. This new development could well overcome the so-called magic triangle of tires, which is certainly one of the key objectives of the tire industry.

Flexural-Fatigue Properties of Sustainable Pervious Concrete Pavement Material Containing Ground Tire Rubber and Silica Fume

With the development of urbanization, pervious concrete has been increasingly used in urban road pavement structures. The objective of this paper was to investigate the effect of stress levels and modifier (ground tire rubber and silica fume) on the fatigue life of pervious concrete and establish the fatigue equations with different survival probabilities. In order to improve the deformability of pervious concrete without sacrificing its strength, ground tire rubber and silica fume were added into pervious concrete. Two kinds of pervious concrete, control pervious concrete and ground tire rubber and silica fume modified pervious concrete, were made in the laboratory. The pervious concrete beam specimens of 100 × 100 × 400 mm were casted, and the static flexural strength and flexural strain of the two kinds of pervious concrete were tested. The fatigue lives of two pervious concretes were tested using MTS fatigue testing machine under four different stress levels (0.85, 0.80, 0.75, and 0.70). The fatigue life was analyzed by two-parameter Weibull distribution. The parameters of Weibull distribution were determined by graphical method, maximum likelihood method and moment method. The Kolmogorov–Smirnov test was used to test the Weibull distribution and the fatigue equations under different survival probabilities were established. The results showed that ground tire rubber and silica fume modified pervious concrete had better deformability while ensuring strength compared to control pervious concrete. The addition of ground tire rubber and silica fume improved the fatigue life of pervious concrete. The two-parameter Weibull distribution was suitable to characterize the fatigue characteristics and predict the fatigue life of pervious concrete. Fatigue equations with different survival probabilities were a good guide for pervious concrete design.

Performance evaluation of polymer modified asphalt (PMA) binders containing ground tire rubber (GTR)

The study presents an experimental evaluation of performance properties of rubberized polymer modified asphalt (PMA) binders to compare two types of ground tire rubber (GTR): normal and treated. Styrene-butadiene-styrene (SBS) modified asphalt binder (PG 76-22) is used as a base PMA binder to produce rubberized PMA binder. The rubberized PMA binders were artificially short-term and long-term aged using the rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were carried out on the binders through the rotational viscometer (RV), the dynamic shear rheometer (DSR), and the bending beam rheometer (BBR). Additionally, the multiple stress creep recovery (MSCR) test was accomplished to investigate the rutting properties. In general, the results of this study indicated that (1) the viscosity properties are found to be dependent on GTR types and amounts, as expected, (2) the rutting properties of PMA binders are expected to be improved through the use of GTR, (3) the addition of GTR is observed to be effective in improving the cracking performances of PMA binder, and (4) in general, the PMA binders with treated GTR showed better performance properties, compared to the PMA binders with normal GTR.

Rotomolding of Foamed and Unfoamed GTR-LLDPE Blends: Mechanical, Morphological and Physical Properties

In this work, a simple method is presented to produce ground tire rubber (GTR) -linear low density polyethylene (LLDPE) compounds and foams via rotational molding. In particular, different GTR concentrations (0 to 50% wt.) were dry-blended with different chemical blowing agent (CBA) content (0 to 1% wt.). From the samples produced, a complete set of characterization was performed in terms of mechanical properties (tensile, flexural and impact), density and morphological properties. The results show that increasing GTR content or CBA content not only decreased both tensile and flexural moduli, but decreased ultimate strength and strain at break. As expected, increasing blowing agent content decreased density. Besides, with respect to impact strength, the value of all samples decreased with the addition of GTR or CBA except for 0.2% wt. CBA of GTR-LLDPE composite foams, which nearly remain at the same level.

Morphological and nanomechanical analyses of ground tire rubber-modified asphalts

Abstract Automobile industries produce more than 5.2 million tons of scrapped tires each year in the United States. Disposal of such a huge amount of waste scrapped tires has become a serious environmental issue. Scopes to use scrapped tires in the form of Ground Tire Rubber (GTR) in pavement industry have been analyzed in recent years. The GTR has potential to improve hot mix asphalt’s performance from the view points of stiffness, resilience and shock absorbance properties. On the other hand, in recent years, researchers have attempted to explain performance of asphalt in terms of its nanomechanical characteristics. In this study, the PeakForce Quantitative Nanomechanical Mapping (PFQNM™) mode of an atomic force microscope has been employed to find basic nanomechanistic properties and the morphology of GTR-modified asphalt binders. A performance grade (PG) binder (PG 64-22) modified with two different grades of GTR (Mesh #30 and Mesh #40) samples have been evaluated in this study. Nanomechanical properties such as adhesion, energy dissipation, deformation, and DMT (Derjaguin, Muller, and Toporov) modulus for the GTR-modified binders have been quantified. Each sample was scanned for three different (5 × 5, 10 × 10, and 20 × 20 µm) areas. The PFQNM™ analyses revealed distinct microstructures and grain distributions among tested additive modified binder samples. Two distinct phases, namely Catana and Peri-phase, were observed in GTR-modified samples, although the DMT moduli were found to be in a close range in these areas. The neat binder showed another phase, named Perpetua, which was missing from the GTR-modified samples. It was observed that modification of asphalt by addition of GTR considerably changes the mechanistic properties of the base binder.

Effect of ground tire rubber on structural, mechanical and thermal properties of flexible polyurethane foams

Flexible polyurethane foams were modified with two kinds of ground tire rubber, untreated and thermo-mechanically reclaimed. A reclamation process was performed in auto-thermal conditions, which reduced the cost of the process and decreased the environmental impact of devulcanization (e.g., emission of gases). The reclamation process was carried out in a continuous manner using a co-rotating twin screw extruder. The foams were prepared by a single step method for the ratio of isocyanate groups to hydroxyl groups equals to one. The ground tire rubber particles were added to a polyol mixture. The impact of the rubber treatment on the properties of resulting polyurethane composites was determined by the analysis of static and dynamic mechanical properties and thermal properties. The incorporation of rubber particles into the polymer matrix caused significant changes in the cellular structure of polyurethane foam, which was confirmed by SEM images. Moreover, a higher content of ground tire rubber in the polyurethane/ground tire rubber foamed composites enhanced their cross-link density estimated from the swelling measurements. It was also confirmed by an increase of glass transition temperature measured by dynamic mechanical analysis and differential scanning calorimetry. Addition of ground tire rubber to polyurethane foams had very positive influence on their thermal stability measured by the temperature corresponding to the 2 % mass loss during degradation of material. Modification increased initial degradation temperature even by 14 °C compared to a reference sample.

Influence of ground tire rubber on the transient loading response of a peat biofilter

The effect of using ground tire rubber (GTR) as an adsorptive material in the removal of a 2:1:1 weight mixture of n-butyl acetate, toluene and m-xylene by using a peat biofilter under different intermittent conditions was investigated. The performance of two identical size biofilters, one packed with fibrous peat alone and the other with a 3:1 (vol) fibrous peat and GTR mixture, was examined for a period of four months. Partition coefficients of both materials were measured. Values of 53, 118 and 402 L kg −1 were determined for n-butyl acetate, toluene and m-xylene in peat, respectively; and values of 40, 609 and 3035 L kg −1 were measured for the same compounds in GTR. Intermittent load feeding of 16 h per day, 5 days per week working at an EBRT of 60 s and an inlet VOC concentration of 0.3 g C m −1, resulted in removal efficiencies higher than 90% for both biofilters, indicating that the addition of GTR did not adversely affect the behavior of the bioreactor. Full removal of n-butyl acetate was obtained for both biofilters. GTR improved the removal of the aromatics in the first part of the biofilter, facilitating lower penetration of the toluene and m-xylene into the bed. A 31-day starvation period was applied and intermittent operation subsequently restarted. In both biofilters, high removal efficiencies after a re-acclimation period of two days were achieved. A shock loading test related to 1-h peaks of three- and four-fold increases in its baseline concentration (0.30 g C m −3) was applied in both biofilters. For the biofilter packed with the peat and GTR mixture, attenuation greater than 60% was observed in the maximum outlet concentration when compared to the biofilter packed with peat alone.

Thermo-rheological behaviour and storage stability of ground tire rubber-modified bitumens

This paper deals with the thermo-rheological behaviour at in-service and handling temperatures (i.e. pumping, mixing, compaction, etc.) of bitumens modified by 9 wt% crumb tire rubber. The use of waste tire rubbers as bitumen modifiers can contribute to alleviate pollution problems derived from discarding scrap tires. Thus, the mechanical characteristics and storage stability of crumb tire rubber modified bitumens (CTRMBs) have been studied as a function of rubber particle size. The addition of ground tire rubber to bitumen increases both the linear viscoelastic moduli and viscosity, at high in-service temperatures, and reduces the storage and loss moduli, at low temperatures, resulting in a more flexible binder in this temperature region. As a consequence, a crumb tire rubber modified bitumen displays enhanced mechanical properties, which improves its resistance to both rutting and fatigue cracking. The presence of insoluble non-spherical particles affects the flow behaviour observed at high temperatures. From the experimental results obtained, it may be concluded that the use of rubber particle sizes lower than 0.35 mm and high shear rates during manufacturing operations is highly recommended. Storage stability of CTRMBs decreases with increasing particle size and storage temperature and takes place by the precipitation of the non-dissolved rubber particles. Only the sample containing rubber particles with a mean particle size of 0.29 mm remains stable under the selected storage conditions.

Thermo-rheological behaviour and storage stability of ground tire rubber-modified bitumens

This paper deals with the thermo-rheological behaviour at in-service and handling temperatures (i.e. pumping, mixing, compaction, etc.) of bitumens modified by 9 wt% crumb tire rubber. The use of waste tire rubbers as bitumen modifiers can contribute to alleviate pollution problems derived from discarding scrap tires. Thus, the mechanical characteristics and storage stability of crumb tire rubber modified bitumens (CTRMBs) have been studied as a function of rubber particle size. The addition of ground tire rubber to bitumen increases both the linear viscoelastic moduli and viscosity, at high in-service temperatures, and reduces the storage and loss moduli, at low temperatures, resulting in a more flexible binder in this temperature region. As a consequence, a crumb tire rubber modified bitumen displays enhanced mechanical properties, which improves its resistance to both rutting and fatigue cracking. The presence of insoluble non-spherical particles affects the flow behaviour observed at high temperatures. From the experimental results obtained, it may be concluded that the use of rubber particle sizes lower than 0.35 mm and high shear rates during manufacturing operations is highly recommended. Storage stability of CTRMBs decreases with increasing particle size and storage temperature and takes place by the precipitation of the non-dissolved rubber particles. Only the sample containing rubber particles with a mean particle size of 0.29 mm remains stable under the selected storage conditions.

Poker chip tests on bituminous concrete

The scope of this work was to obtain the constitutive relations for bituminous concrete loaded in hydrostatic tension, since this is usually the most critical loading mode, i. e., the ultimate strain is less and the ultimate stress is greater than for any other mode of tension loading. Four bituminous concretes were tested using the poker-chip configuration. All of the procedures were the same except that asphalts from two sources were used, one of these asphalts was modified with latex, and ground rubber aggregate was added to the fourth mixture. The variation of ultimate hydrostatic tensile strain was small, but the variation of stress was significant as a function of rate of loading, binder type, or binder additive. The addition of ground tire rubber to the aggregate increased the ultimate strain 25%, and more importantly, increased the mechanical aging index from 0.57 to 0.81.